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Abstract Detail

Genetics Section

Snow, Allison [1], Sweeney, P. M. [1], Lang, Nguyen [2], Buu, Bui [2].

Hybrids between weedy and cultivated rice (Oryza sativa) in the Mekong Delta of Vietnam exhibit heterosis: implications for rapid evolution in weedy rice.

WEEDY rice (Oryza sativa) hybridizes with cultivated rice (also O. sativa) in many regions of the world, but little is known about variation in the fitness and vigor of early and advanced-generation crop-weed hybrids. We hypothesized that crop-weed hybrids would perform better than their weedy parents due to heterosis. The relative fecundity of crop-weed hybrids is expected to influence rates of crop allele introgression, and certain fitness-enhancing crop alleles could accelerate this process. We compared the fecundity of F1, F2 and BC1 progeny of three weedy rice accessions (W1, W2, W3) crossed with two local rice cultivars (IR-64, OM-1490) with that of their respective weedy parents in the Mekong Delta of Vietnam. Fecundity, measured as seed per plant, was evaluated in two fields, one flooded and one non-flooded. In all cases, F1, F2, and BC1 progeny performed as well or better than their weedy parent. Non-flooded plants had higher fecundity than flooded plants, and numerous interactive effects were significant in ANOVAs. The F1 and F2 progeny of both W1 and W2 had higher fecundity than their respective weedy parents. In addition, the BC1 progeny of W2 out-performed the F1 and F2 progeny and produced nearly twice as many seeds as the weedy parent. In contrast, the fecundity of W3 progeny was not significantly different from their weedy parent. Therefore, F1, F2, and BC1 progeny can have enhanced fecundity relative to their weedy parents, depending on the weedy accession tested, suggesting that heterosis can boost rates of introgression after hybridization has occurred. If this effect is common in rice fields with weedy rice populations, rates of crop allele introgression may be greater than one would expect based solely on the small proportion of F1 hybrid seeds that are produced on weedy rice plants.

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1 - Ohio State University, Department of Evolution, Ecology and Organismal Biology, 300 Aronoff Laboratory, 318 W. 12th Ave., Columbus, Ohio, 43210-1293, USA
2 - Cuu Long Rice Research Institute, Omon, Cantho, , Vietnam

gene flow
weedy rice
cultivated rice

Presentation Type: Oral Paper:Papers for Sections
Session: 34-13
Location: 350/Holt
Date: Tuesday, August 1st, 2006
Time: 11:30 AM
Abstract ID:662

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